Are you sure this isn't a source control issue? Visual Studio doesn't, as far as I'm aware, change the case of filenames from what you've told it. If you rename a file it correctly renames it on disk.
However, Windows plus some source control tools treat PascalCase.jsx and pascalCase.jsx as the same file, so if you rename from one to the other your source control won't recognize a change. You'll have the renamed file locally, but even after a sync you'll still have the original filename in source control. Then if you do a clean checkout you'll discover the filename has reverted. Git does this. One workaround is to delete the file and recreate it
This may not be what's happening, it's a little unclear from your question!? Perhaps you can give more details on when the file gets renamed?